Thread-mold for concrete pipe



J. G. ZWICKER.

THREAD mow FOR CONCRETE PIPE,

I APPLICATIQN FILED SEPT. 23, I918- 1,365,014;, Patented Jan. 11,1921.

6 Mb r 6 f1 M Z WITNESS A TTORNEYS PATENT QFFICE.

JULIUS G. Z'W'IGKER, 6F BERKELEY, CALIFORNIA.

THREAD-MOLD FOR CONCRETE PIPE.

Specification of Letters Patent.

Patented Jan. 11, 1921.

Application filed September 23, 1918. Serial No. 255,343.

1 '0 all to item it may concern Be it known that I, JULIUS Gr. ZWICKER, a citizen of the United States, residing at Berkeley, in the county of Alameda and State of California, have invented certain new and useful Improvements in Thread- Molds for Concrete Pipe, of which the following is a specification.

My invention relates to the art of making concrete-pipe, the ends of which are threaded, so that the pipe sections may be screwed together.

Threaded concrete-pipe, though apparently quite simple in conception, is, nevertheless, not easy to produce successfully, the chief drawback being the difficulty of making the threads sufficiently perfect to insure a tight joint. Manifest-1y, to even approximate this result, much will depend upon the molds used. Frangible molds, such, for ex ample, as those made of plaster-of-Paris, which yield an advantage in separating the molded product, are, by reason of their structure, necessarily not accurate; and, on the other hand, metal-molds, when made of suchmaterial as brass or iron, are not per feet in the casting and require to be machined besides being oorrodible and relatively heavy.

Experience has demonstrated, however, that metal-molds are better than frangible molds, for the disadvantage which first at tended their use, namely, that of separating the molded product by screwing it out, has been overcome by various expedients, such, for example, as coating them with a lubricant or with a thin layer of paraffin or other readily liquefiable substance and applying heat.

My present invention, therefore, involves a metal mold, but of a novel structure, namely a thread portion of Babbitt metal and a backing portion of aluminum, cast one upon the other, to form a practically binding union. One object of the invention is to provide a thread-mold for concrete-l pipe sections, the threads of which are accurate in the casting, thereby dispensing with machining and its consequent expense. Another object is to provide such a mold the thread portion of which can be inexpensively renewed. Other objects are, lightness, rigidity, and durability.

The nature of my thread-mold and the manner in which it is made will now fully appear from the following description, read in connection with the accompanying drawings, in which- Figure l is a cross sectional view of my thread-mold for making the male thread end on the pipe section.

Fig. 2 is a cross sectional view of said mold for making the female thread end on said section.

Fig. 3 is a cross-section of one side of the master-mold, showing the aluminum component of the male-thread-mold in place to form one wall ready to receive the molten Babbitt metal which forms the other component of said tl'iread-mold.

Fig. 42 is a cross section of one side of the master mold showing the aluminum component of the female thread-mold in place to receive the Babbitt-metal component.

1 In Fig. 1, the male-thread-mold A, is an annular body comprising a Babbitt-metal, threaded component 1 and an aluminum backing component 2.

In Fig. 2 the female-thread mold A is an annular body comprising likewise a Babbitt-- metal, threaded component 1 and an aluminum backing component 2. The aluminum backing components 2 and 2' are formed at each end with angular portions, those at one end extending oppositely to those at the other end. The outer edges of these angular portions are formed with angular terminal lips against which the Babbitt-metal, lies, thereby protecting the relatively softer metal and preventing rubbing in the press in which the molds are used. Each mold, both at top and bottom is square with respect to its axis, thus providing for square shoulders at the end of the molded pipe section and at the base of its threaded portion. This is important in threaded concrete pipe, for it insures the close abutment of the threaded ends, which, to be tight, must fit with all possible accuracy.

The method of making these thread-molds is illustrated in Figs. 3 and 4.

The aluminum component is first cast in any suitable mold, and is then placed in position to form one wall of the master-mold in which the Babbitt-metal component is cast.

Thus, in Fig. 3, it opposes, in spaced relation, the threaded metallic wall 3 of the master mold being supported on said wall 3 at its top and resting at its base on the top of a support 4. A hole 5 is drilled in the top of the aluminum component 2 and through this hole the Babbitt-metal is poured until it fills the space between the aluminum component 2 and the threaded wall I have not in Fig. 3 shown the Babbitt-metal, deeming it clearer to omit it, but it will be understood that when poured into the mold space, it will thereby have formed in it the necessary internal threads 6 shown in Fig. 1.

Likewise in Fig. 4, where the aluminum component 2 is properly seated in spaced relation to the threaded master mold wall 3 and rests on the support 4:, the Babbittmetal poured in through the hole 5 in the top of the aluminum component 2 will have the necessary external threads 6 formed in it, as shown in Fig. 2. The terminal lips of the aluminum component, in addition to protecting the babbitt, as hereinbefore mentioned, serve as end closures for the molding space.

is aluminum and Babbitt-metal have different coeriicients of contraction, it results that the two will shrink together to form a close or binding oint, the aluminum shrinking in Fig. 3, upon the Babbitt-metal and in Fig. 4n, the atmospheric pressure will cause the Babbitt-metal to follow up the shrinking aluminum, so that in both cases the union is very close. Practice has shown that in order to insure close union, the aluminum component should, at the time of pouring in the Babbitt-metal, be of approximately the same temperature as the molten Babbittmetal.

The Babbitt-metal when poured into the master-mold space will form very perfect threads which need no subsequent machining, and it has the additional advantage of being readily melted off and used over again,

if for any reason its threads should be spoiled. The Babbitt-metal alone would not serve for the larger sizes of pipe, as it is not sufliciently rigid, but the aluminum backing gives it the required strength. Nor would aluminum alone serve the purpose, as it does not lend itself to accurate casting. But as a backing for the mold its want of accuracy is negligible, while, at the same time, it furnishes the required rigidity, is not liable to be corroded and gives lightness to the mold.

I claim 1. A thread-mold for the ends of concretepipe sect-ions comprising a threaded component of Babbitt-metal, and a backing component of aluminum, the aluminum component having both its ends formed with relatively oppositely extending angular portions having angular terminal lips against which the extremities of the Babbitt-metal component.

lie.

2. A thread-mold for the ends of concretepipe sections, comprising a threaded component of Babbitt-metal and a backing component of aluminum, the aluminum component having both its ends formed with relatively oppositely extending angular portions having angular terminal lips against which the extremities of the Babbitt-metal component lie, said pipe forming closures for the pouring of the Babbitt-metal, and said angular portions at one end having a hole for pouring in the Babbitt-metal.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

JULIUS Gr. ZWICKER. Vitnesses WM. F. BOOTH, D. B. RICHARDS. 

